The invention relates to a supply circuit for a corona ignition device, as well as to a corona ignition system with a corona ignition device and such a supply circuit.
U.S. Publication No. 2004/0129241 A1 describes the ignition of fuel in a combustion chamber of an internal combustion engine by means of a corona discharge generated in the combustion chamber. Such a corona ignition device comprises a center electrode held by an insulator body, which forms a capacitance together with an outer conductor enveloping the insulator body or the walls of the combustion chamber which are at mass potential and provide the counter-electrode. The insulator, which surrounds the center electrode, and the combustion chamber with its contents act as the dielectric of this capacitance. Depending on the stroke of the piston, the combustion chamber contains air or a fuel-air mixture or an exhaust gas.
This capacitance is part of an electrical resonant circuit, which is excited with a high-frequency alternating voltage of 10 kV or more. This alternating voltage is generated by a high-frequency generator, e.g., by a transformer with center tap.
As a rule, most vehicles have an on-board electrical system voltage of only 12 V. Theoretically, it is possible to use such an on-board electrical system voltage as input voltage for the high-frequency generator of a corona ignition system. However, this is very expensive. This is why corona ignition systems in vehicles usually contain a supply circuit that generates a supply voltage from the on-board electrical system voltage of about 100 V to 400 V for the high-voltage generator.